Python pip 模块，commands_dict() 实例源码

def bootstrap(tmpdir=None):
    # Import pip so we can use it to install pip and maybe setuptools too
    import pip
    from pip.commands.install import InstallCommand

    # Wrapper to provide default certificate with the lowest priority
    class CertInstallCommand(InstallCommand):
        def parse_args(self, args):
            # If cert isn't specified in config or environment, we provide our
            # own certificate through defaults.
            # This allows user to specify custom cert anywhere one likes:
            # config, environment variable or argv.
            if not self.parser.get_default_values().cert:
                self.parser.defaults["cert"] = cert_path  # calculated below
            return super(CertInstallCommand, self).parse_args(args)

    pip.commands_dict["install"] = CertInstallCommand

    # We always want to install pip
    packages = ["pip"]

    # Check if the user has requested us not to install setuptools
    if "--no-setuptools" in sys.argv or os.environ.get("PIP_NO_SETUPTOOLS"):
        args = [x for x in sys.argv[1:] if x != "--no-setuptools"]
    else:
        args = sys.argv[1:]

        # We want to see if setuptools is available before attempting to
        # install it
        try:
            import setuptools  # noqa
        except ImportError:
            packages += ["setuptools"]

    delete_tmpdir = False
    try:
        # Create a temporary directory to act as a working directory if we were
        # not given one.
        if tmpdir is None:
            tmpdir = tempfile.mkdtemp()
            delete_tmpdir = True

        # We need to extract the SSL certificates from requests so that they
        # can be passed to --cert
        cert_path = os.path.join(tmpdir, "cacert.pem")
        with open(cert_path, "wb") as cert:
            cert.write(pkgutil.get_data("pip._vendor.requests", "cacert.pem"))

        # Execute the included pip and use it to install the latest pip and
        # setuptools from PyPI
        sys.exit(pip.main(["install", "--upgrade"] + packages + args))
    finally:
        # Remove our temporary directory
        if delete_tmpdir and tmpdir:
            shutil.rmtree(tmpdir, ignore_errors=True)